Device for perforating casing of a well and cracking cement surrounding the casing



July 24, 1962 R. J. GOODWIN DEVICE FOR PERFORATING CASING OF A WELL AND CRACKING CEMENT SURROUNDING THE CASING Filed June 26, 1958 INVENTOR.

.QOEEPT J. GOOD/VIN ilnited rates Parent @fifire 3,045,753 Patented July 24, 1962 3,045,753 DEVICE FOR PERFORATING CASlNG OF A WELL AND CRACKING CEMENT SURRGUNDING Til-E CASING Robert J. Goodwin, Oaitmont, Pa., assignor to Gulf Research & Development Company, Pittsburgh, Pa, a corporation of Delaware Filed June 26, 1958, Ser. No. 744,796 Claims. (Cl. 166-55) The present invention pertains to new and useful improvements in devices for perforating well casing of the type used in oil wells, and more particularly pertains to devices of such character adapted to perforate, deform, and readily disengage from the well casing without passing entirely through the performation made thereby.

. Special utility for devices according to the present invention resides in carrying out the operation described in U.S. application Serial No. 501,063, filed April 13, 1955 by Abraham I. Teplitz, entitled Method of Completing Wells which discloses a well completion process wherein a cementitious sheath is formed in the annular space between a poorly consolidated producing formation and the well casing, and thereafter perforating the casing at a plurality of positions and applying sufficient deforming stress to the well casing so as to result in a plurality of minute fissures in the cementitious sheath, so that the well can produce through the fine network of fissures or fractures in the cementitious sheath and the perforations in the well casing. The application states that the perforations and the application of stress to the well casing can be accomplished by forcing casing piercing elements against the casing either hydraulically or mechanically, or that such perforating and stress application can be by the use of gun perforators of such character that the bullets strike the casing with sufficient force to perforate the same but insufficient to pass entirely therethrough so that the bullets either rebound into the interior of the casing or are left in a position where they can be readily removed by scratchers or the like.

It is the specific aim of the present invention to provide a device such as can be employed as a bullet or projectile in conjunction with conventional gun perforators, or which can alternatively be used with mechanical or hydraulic systems such as disclosed in my pending U.S. application Serial No. 706,498, filed December 31, 1957, now U.S. Patent No. 2,974,727 entitled Well Perforating Apparatus, for carrying out the well completion process discussed briefly in the preceding paragraph and described in substantial detail in the aforementioned U.S. application Serial No. 501,063.

Another purpose of the invention is to provide a device of the character specified above which will have a minimum tendency to weld or otherwise seize with the well casing so as to avoid any difiiculties whatever in removing or disengaging the device from the well casing. That such seizure or seizing can readily occur when a penetrating or perforating device is forced into a casing Wall will be appreciated upon consideraton of U.S. Patent No. 2,768,- 552 issued October 30, 1956 to MacDonald. The purpose of the devices disclosed in the patent is to achieve a welding or seizure, and consequently the distinctions between the devices of the patent and embodiments of the present invention are of a vital and critical nature, as those distinctions minimize tendency to weld or seize.

Broadly, a device embodying the principles of the present invention involves a shank carrying a casing perforating and deforming head at one end, such head being substantially circular in transverse peripheral configuration and having a surface convex from the sank; such head terminating in a pyramidal tip having a base dimension less than about one-half the maximum diameter of the head, and having a volume less than that of a right circular cone of equal base and height, with the surface of the head and preferably also that of the tip portion of the head being substantially unpolished. Preferred 5 embodiments of the invention also involve the head having a surface exposed portion of substantial axial extent that has a substantially softer surface hardness than adjacent surface portions of the head, whereby the device will reveal on inspection after use the axial extent of the head that has engaged a well casing. Also, preferred embodiments of the invention involve the surface of the head and, preferably, also the tip having an unpolished ,surface, such surface being rough to the degree of that normally possessed by a machined, cast, or forged surface, either with or without a subsequent surface hardening treatment.

The invention will be best appreciated upon reference to the accompanying drawings illustrative of preferred embodiments of the invention; wherein FIGURE 1 shows a device according to the invention in side elevation with the device shown in the position after which the same has perforated and deformed a well casing to cause fracturing of a cementitious sheath, the well casing and the cementitious sheath being shown in vertical section;

FIGURE 2 is an enlarged end view of the device shown in FIGURE 1, with the hidden portions of the inserts being shown in dashed outline;

FIGURE 3 is a side elevational view of the structure shown in FIGURE 2;

FIGURES 4 and 5 are respectively end and side elevational views of a modified form of the device shown in FIGURES 1, 2, and 3;

FIGURES -6 and 7 are respectively end and longitudinal sectional views of yet another modification of the device:

FIGURES 8 and 9 are respectively end and slide elevational views of still another modification of the device wherein the piercing tip is of three-sided pyramidal shape;

and

FIGURES 10 and 11 are respectively end and side elevational views of a further modification of the device.

Referring to FIGURES 1, 2, and 3, the device of the invention is designated generally at 10, the same being comprised of a cylindrical shank 12, one end portion of which constitutes a perforating and deforming head 14. The head 14 has a surface 16 that is convex from the shank 12, as shown, with such surface 16 preferably being of spherical configuration where the sphere has a radius equal to that of the shank 12.

The head 14 terminates in a conical perforating or piercing tip 18 having a base diameter that is less than the maximum diameter of the head 14. As best shown in FIGURE 3, the surface of the conical tip 18 does not smoothly merge with the surface 16, the transition between such surfaces being essentially abrupt as indicated at 20 for a purpose explained later.

The device 10 is provided with a plurality of circumferentially spaced wedge-shaped inserts 22 which extend the entire length of the shank 12 and which terminate at the position of maximum diameter of the head 14. With the exception of the inserts 22, the shank 12 and the convex portion of the head 14 are of integral construction, and are preferably made of drill rod or tool steel having a heat treated hardness of about Rockwell 0-50 to about Rockwell C-60 which is quite suitable for conventional hardening treatment after the integral construction has been formed by machining. The conical tip 18 of the head 14 can be integral with and of the same composition as the remaining portion of the head 14, or when it is desired that the tip 18 be of still harder characteristics, the same can be formed of alloys such as nickel, manganese, chromium, and vanadium alloy steels and secured to the balance of the head 14 by welding, shrink fitting and/ or proper shaping of the two points prior to any final shaping steps that may be necessary.

The inserts 22 are of such character as to possess a substantially lesser surface hardness in the completed device '10 than adjacent portions of the shank 12 and the head 14. Conveniently, the inserts can be low carbon steel or titanium-low carbon alloy steel. When the device 10 is to be subjected to a final surface hardening treatment, the inserts 22 can be low carbon or stainless steel for the reason that such material does not undergo as marked an increase in surface hardness as do the materials from which the other portions of the shank 12 and the head 14 are formed. The inserts 22 are secured in complementary grooves in the shank 12 by welding or undercutting and shrink fitting.

Though not absolutely imperative in all instances, it is greatly preferred that the surface of the head 14 not be polished or otherwise given any treatment resulting in anything approaching a mirrorlike finish. The preference for a surface possessing at least a modicum of roughness is not fundamentally motivated by any desire for economy or lack of esthetic taste, but is founded upon the cogent reason that a somewhat rough surface has a greater ability to deform the pipe, as well as lesser likelihood of cementing or seizing with other metallic surfaces with which the same may be brought into sliding contact under great pressure. In general, it is preferred that the surface 16 of the head 14 and preferably also the surface of the conical tip 18 have a surface rougher than a surface fineness of S to 60 micro inches as measured on a profilometer.

Attention is now directed to FIGURE 1 wherein the function of the device 10 is depicted. A well casing is indicated at 24, such well casing 24 being surrounded by an annular cementitious sheath 26 that is interposed between the well casing 24 and a poorly consolidated oil producing formation 28. The device 10 is shown in a position wherein the same has pierced or perforated the well casing 24 at 30 and deformed the well casing 24 about the perforation 30 by bulging the well casing 24 about the perforation 30 as indicated at 32 so as to enlarge the perforation 30. The device 10 is shown in the position of maximum desired advance towards the exterior of the well casing 24. It will be noted that the action of the device 10 upon the well casing 24 is such as to cause a network of fine fractures or fissures 34 in the cementitious sheath 26 through which fluids from the producing formation 28 may pass into the well casing 24 via the perforation 30.

FIGURE 1 does not depict the means by which the device 10 is forced against or caused to impinge upon the well casing 24 inasmuch as such means are not the subject of this invention, it being understood that such means can be hydraulic or mechanical means for forcing the device 10 against the well casing 24, or that such means can be an explosive charge such as that employed in gun perforators. After use of the device 10, the same can be recovered from the well in which the well casing 24 is disposed and visually inspected in order to ascertain whether the device 10 had penetrated into the well casing 24 substantially farther than that shown in FIGURE 1, the ease of such visual inspection being greatly facilitated by the inserts 22, inasmuch as the surface hardness of such inserts 22 is such as to readily bear the imprint of any forcible contact with the well casing 24.

FIGURES 4 and illustrate a modified embodiment of the invention comprising a shank 36 and a head 38. The head 38 has a diameter substantially greater than that of the shank 36, :and in this form of the invention, the head 38 is provided with a plurality of circumferentially spaced inserts 40 that have surfaces constituting a portion of the convex surface 42 of the head 38. With the exception of the inserts 40, the head 38 including the piercing tip 44 thereof is of integral construction. In this form of the invention, the surface of the tip 44 smoothly merges with the surface 42 of the remainder of the head 38, though the outer extremity of the tip 44 is or closely approaches a conical configuration. The shank 36 need not be integral with the head 38, in which case the same can be separately fabricated and thereafter suitably secured by welding or the like to the head 38, and in which case the shank 36 can be formed of softer material than the head 38. As will be understood, the inserts 40 are constituted of a material corresponding to the inserts 22 of the previously described embodiment of the invention, with the remaining portions of the head 38 being constituted of a material such as that previously described in conjunction with the head 14.

FIGURES 6 and 7 disclose an embodiment of the invention that is similar to the embodiment shown in FIG- URES 1, 2, and 3. The form of the device shown in FIGURES 6 and 7 includes a shank 46 having a convex end portion constituting a deforming head 48 to the latter of which is secured a conical perforating or piercing tip 50. The device shown in FIGURES 6 and 7 is similar in surface configuration to that shown in FIGURES 1, 2, and 3, and is otherwise the same, except in that the device shown in FIGURES 6 and 7 does not include inserts such as the previously described inserts 22 and in that the surface of the head 48 is rough to such an extent as to be rougher than a surface having a fineness of 50 to 60 micro inches as measured by a profilometer. The surface roughness of the head 48 serves the dual functions of preventing welding or seizing with well casing and that of making visually apparent the axial extent of the head 48 that has forcibly engaged a well casing. In connection with the latter-mentioned function of the rough surface of the head 48, it will be apparent that a rough surface more readily bears the imprint of engagement with another metallic surface under great pressure than does a relatively smooth surface.

The form of the invention illustrated in FIGURES 8 and 9 corresponds substantially to that shown in FIG- URES 6 and 7 and comprises a shank 52, and a deforming head 54 surmounted by a pyramidal piercing tip 56. While a conical tip may be considered a pyramidal tip of an unlimited number of sides, and while the term pyramidal tip is employed in such broad sense in the claim, the pyramidal tip 56 corresponds more closely with the sense with which the term is normally employed in that the pyramidal tip 56 is three sided. The purpose of the pyramidal configuration of the tip 56 is that the edges 58 constituting the boundaries between adjacent sides of the tip 56 serve to either cut or deform the edges of the performations formed in a well casing so that the perforation is enlarged more readily upon further deformation of the well casing by the enlarged portion of the head 54. Generally speaking, it is preferred that the pyramidal tip have either an unlimited number of sides so as to be more appropriately considered conical, or that the same have relatively few sides such as from three, such as shown in FIGURES 8 and 9, to say six sides.

Referring now to the further embodiment of the invention shown in FIGURES 10 and 11, it will be seen that the same comprises a shank 60 and a head 62 surmounted by a perforating or piercing tip 64. The head 62 is provided with a plurality of circumferentially spaced inserts 66. Except for the position of and the shape of the inserts 66, the structure shown in FIGURES 10 and 11 is identical with that shown in FIGURES 1, 2, and 3. From the preceding discussion, it will be seen that the differing position of the inserts 66 affords an indication of lesser extents of penetration than in the case of use of the device shown in FIGURES l, 2, and 3.

In all of the previously described embodiments of the invention, it is preferred that the apex angle of the piercing tips be in the range of from about 30 degrees to about 60 degrees, it having been found that a piercing angle of s ar about 45 degrees is especially useful. In order to effect readily penetration and also in order to lessen the likelihood of a Weld or seizure of the device occurring with the well casing, the piercing or perforating tip should be sufii-.

ciently pointed so as to have a substantially lesser volume than would a right circular cone of equal base and height, while on the other hand, the tip should not be so pointed considering the relative hardnesses of the well casing 24 and the tip that appreciable blunting of the tip occurs during use of the device. Generally speaking, it is preferred that there be an abrupt change in curvature at the juncture of the tip and the remainder of the head, as such an abrupt transition tends to prevent welding.

It is generally preferred in the use of devices of the present invention that the overall dimension thereof be so selected with respect to the Wall thickness of the well casing 24 that the maximum diameter of the perforating and deforming head be greater than approximately twice the wall thickness. Also, it is preferred that the piercing tip have an effective height approximately equal to the wall A thickness of the casing 24.

Many other modifications of the illustrated embodiments of the invention will readily occur to those skilled in the art, and accordingly reference to the appended claims should be made in order to ascertain the actual scope of the invention.

-I claim:

1. A device operable Within a well casing and adapted to perforate the casing, deform the casing to crack cement surrounding the casing, and readily and completely disengage from well casing having a wall thickness of about one-half the diameter of the device for production of fluids through cracks in the cement, comprising a cylindrical shank having a central axis and carrying a casing perforating and deforming head at one end, said head having a central axis coincident With the central axis of the shank and being substantially circular in transverse peripheral configuration, said head having a surface convex from the shank, said surface being longitudinally convex With respect to the central axis of the head, said head terminating in a pyramidal tip having a central axis coincident with the central axis of the head and having a maximum base dimension less than about one-half the maximum diameter of the head, the apex angle of the tip being between degrees and 60 degrees, said head other than the tip having a rough outer surface, whereby the tip of the head can pierce through the wall of a well casing with further axial movement of the head serving to bulge the wall of the casing about the perforation without seizure between the wall of the casing and the device.

2. A device operable within a Well casing and adapted to perforate, deform, and readily disengage from well casing having a wall thickness of about one-half the diameter of the device, comprising a shank having a central axis and carrying a casing perforating and deforming head at one end, said head having a central axis coincident with the central axis of the shank, and being substantially circular in transverse peripheral configuration, said head having a surface convex from the shank, said surface being longitudinally convexwith respect to the central axis of the head, said head terminating in a pyramidal tip having a central axis coincident with the central axis of the head and having a base dimension less than about onehalf the maximum diameter of the head, said tip having a volume less than that of a right circular cone of equal base and height, at least the tip of said head having a har ness in excess of about Rockwell C-5O to about Rockwell C-60, a surface exposed portion of said head of substan' tial axial extent being of substantially softer surface hardness than adjacent surface portions of the head, such portion of the head being adapted to reveal on inspection the axial extent of the head that has engaged a Well casing, said head including a cylindrical section, said surface exposed portion of the head being comprised of a substantially wedge-shaped insert in the cylindrical section of the head.

3. A device operable within a well casing and adapter to perforate, deform, and readily disengage from Well cas ing having a wall thickness of about one-half the diam eter of the device, comprising a shank having a centra axis and carrying a casing perforating and deforming hear at one end, said head having a central axis coincident Witl the central axis of the shank, and being substantially cir cular in transverse peripheral configuration, said heac having a surface convex from the shank, said surface being longitudinally convex with respect to the centra axis of the head, said head terminating in a pyramidal tip having a central axis coincident with the central axis of the head and having a base dimension less than about onehalf the maximum diameter of the head, said tip having volume less than that of a right circular cone of equal base and height, at least the tip of said head having a hardness in excess of about Rockwell C-50 to about Rockwell C-60, a surface exposed portion of said head of substantial axial extent being of substantially softer surface hardness than adjacent surface portions of the head, such portion of the head being adapted to reveal on inspection the axial extent of the head that has engaged a well casing, said surface exposed portion of the head being an insert in the head and having a surface constituting a part of the convex surface of the head.

4. A device for perforating the casing of a well and deforming the casing to crack the cement surrounding the casing for production of well fluids through the thus deformed cement comprising a cylindrical shank having a diameter at least twice the thickness of the casing to be perforated, a substantially hemispherical convex head at one end of the shank, a pyramidal tip permanently extending from the hemispherical head whereby on disengagement of the device from the well casing the pyramidal tip remains integral with the shank, the pyramidal tip terminating in a point in alignment with the central axis of the shank and having an apex angle between 30 degrees and 60 degrees, said tip having a maximum dimension across the base thereof less than about one-half the diameter of the hemispherical head, and a height approximately equal to the wall thickness of the casing.

5. A device for perforating the casing of a Well and deforming the casing to crack cement surrounding the casing for production of Well fluids through the thus formed cracks in the cement comprising a cylindrical shank of a diameter at least twice the thickness of the casing to be perforated, said shank having a rounded end, a pyramidal tip permanently extending from the center of the rounded end of the shank whereby on disengagement of the device from the well casing the pyramidal tip remains integral with the shank, said tip having an apex angle between 30 degrees and 60 degrees, the maximum dimension across the base of the tip being less than about one-half the diameter of the shank and the height of the tip being approximately equal to the thickness of the casing, longitudinal inserts in the shank forming an exposed portion of the outer surface thereof, said inserts being of a material softer than the remainder of the shank whereby on removal of the device from the well the inserts reveal the axial extent that the shank has engaged the well casing.

References Cited in the file of this patent UNITED STATES PATENTS 724,904. Mack Apr. 7, 1903 1,497,919 Layne June 17, 1924 1,706,430 Wilson Mar. 26, 1929 2,315,437 Luccous Mar. 30, 1943 2,381,929 Schlumberger Aug. 14, 1945 2,400,878 Dunn May 28, 1946 2,426,106 Kinley Aug. 19, 1947 2,540,122 Kinley Feb. 6, 1951 2,612,108 Schmidt Sept. 30, 1952 2,896,718 Kibby June 28, 1959 2,974,727 Goodwin Mar. 14, 1961 

